The present invention relates to an improved chemical process, more particularly, to a halogen exchange reaction whereby chlorine is replaced by fluorine.
Halogenated lower aliphatic hydrocarbons in which halogen is fluorine or a combination of fluorine and chlorine have become increasingly important commercially in recent years as refrigerants, blowing agents for foamed plastics, and as monomers. These compounds are made industrially by the catalytic substitution of fluorine for other halogen, usually chlorine, with hydrogen fluoride. A number of metal fluorides and halogen fluorides have been used as catalysts in these reactions. The use of anhydrous HF in such reactions has been considered essential to practical operability. The more readily available and cheaper aqueous hydrofluoric acid would, of course, be preferred over the anhydrous material if these fluorination processes could be adapted to its use, not only for economic reasons, but, in many cases, also for added convenience in handling.